Pedal feel after fitting 8 pot brembos?

[forty3]

After fitting a complete set of rs4 brakes The brake pedal now travels much further than it used to and doesn't feel as positive.

Is this simply an effect of having 8 pots or is there something wrong?

The system is completely bled as I went round twice just to make sure.

I did have an issue with the rear handbrake not releasing (Carista wouldn't work) and got around this by putting the car in neutral and manually releasing the handbrake using the usual button inside the car.

Another thing to mention is that the front wheels wouldn't clear the new Brembos byut luckily I had already ordered some spacers. I thought the front brakes were a straight swap?

 

[xpoweruk]

This should be of help

http://www.audizine.com/forum/showt...er-Cylinder-Upgrade-for-Big-Brake-Kits-Thread

 

[Mario]

Chances are the overall area of the 8 pots is greater than the area of the old calipers you had, so to move the pistons the same distance you need to displace more fluid. To do that you need to push the pedal further.

The only real fix is a larger master cylinder which can displace more fluid for the same stroke.

 

[forty3]

This should be of help

http://www.audizine.com/forum/showt...er-Cylinder-Upgrade-for-Big-Brake-Kits-Thread

Brilliant info. Thanks a lot!

 

[bobby singh]

I found braided lines helped a lot in my case but I have 6 pots not 8

 

[forty3]

I replaced the brake lines as part of the upgrade to ones from HEL performance so don't think thy're the issue.

 

[Cerbera9]

I would re-bleed the brakes again as It can take a couple off attempts to get all the air out of the system properly. I had to to this a couple of times with my 6pot after fitting changing all the fluid and now the feel is spot on.

 

[AudiLeon]

How are you bleeding the brakes? Foot pump method?

 

[forty3]

Used a Gunson easy bleed kit and on the second round of bleeding I got some help and also depressed the brake pedal a couple of times per corner.

 

[forty3]

After reading through xpoweruk link I've done a bit of digging and I think I've found people who have fitted a complete rs5 master cylinder and servo into their S4 although it isn't completely clear as the original link shows someone mating an rs5 master to a b8 servo.

Anyone else done this?

 

[xpoweruk]

B8.5 is different to the B8 so they have to use B8 servo

 

[forty3]

In the original thread on audizine (where the guy fits the brakes and notices the pedal http://www.audizine.com/forum/showthread.php/733947-RS5-Brakes-Upgrade) someone replied saying they had fitted an rs5 servo and master cylinder but I can't find any further information on the straight swap.

 

[forty3]

Ignore my last post. The link is wrong!

Here's what I was referring to http://www.audizine.com/forum/showthread.php/681890-RS5-Brakes?highlight=master+cylinder

 

[xpoweruk]

Looks like that thread was a month or so before the one I posted.
The chap that points out the RS5 master/booster started the thread about the RS5 master fitting the B8 booster about a month later.
IIRC the RS5 booster has something on it that isn't compatible with the S4

edit

RS5 has an external vacuum pump, from what I am told because it's a high-revving, NA engine.

edit 2

RS5 Booster and master combination works. Unfortunately I learned it the hard way. We put it in, I started the car and pedal felt like a rock, no boosting at all. I panicked and had the B8 booster overnighted. We put that one in and it was the same thing! No boosting. So, it turned out the ABS had to be reset with an OBD2. Should I have known that I would have had a nice silver RS booster VS black B8 one.

I have the RS5 Booster for sale by the way....$250 shipped.

So either the B8 booster with RS5 master or RS5 Master & booster seem to be the known working options

 

[Zafi]

You will find you get great feel to the brakes albeit with greater travel.
Conversely if you use a master cylinder which is too large you get no feel at all, a wooden pedal.

 

[forty3]

So I contacted the guy off Audizine about fitting an RS5 master cylinder and this is the reply I got:

I had no issues using either part made the car braking system awesome. The rear brakes are the same size as the RS5 so there is no issues there. I tracked the crap out of the car with that setup. I think you will love it. I did have a shop install the parts, mainly I didn't have time to do it and I remember them telling me they "needed" special tools, Not sure real that is.
Matt

 

[Stu2w]

I have the 8 pot set up too, my pedal travel never changed. I did carry out a full brake fluid change tho. Drained the system completely then started from the rear.